I got a three year-old computer for $50 for my dad who gave it to his brother, who is learning how to use it mostly from his grandson.
Dad says the spam, spyware, and viruses are a problem. I said try the free stuff.
Here's the short list of free programs I use every day, either at home or at work:
Ad-aware and Windows Defender
Firefox and Thunderbird
Copernic Desktop search
Evernote, for taking notes and clipping weblinks and whatever